Hydraulic pump control system



Dec. 10, 1968 H. N. UNDERWOOD ETAL 3,415,053

HYDRAULIC PUMP CONTROL SYSTEM Filed April 26, 1967 2 Sheets-Sheet l Q- I T 32 :3

AG/TA TOR breri'NZbLCiTZUOOd 0 .Eonald HHaas 1968 H. N. UNDERWOOD ETAL 3,415,058

HYDRAULIC PUMP- CONTROL SYSTEM Filed April 26, 1967 2 Sheets-Sheet 2 MO TOP United States Patent 3,415,058 HYDRAULIC PUMP CONTROL SYSTEM Herbert N. Underwood, Chicago, Ill., and Ronald H.

Haas, Lansing, Mich., assignors to Borg-Warner Corporation, Chicago, 11]., a corporation of Illinois Filed Apr. 26, 1967, Ser. No. 633,921 Claims. (Cl. 60--53) ABSTRACT OF THE DISCLOSURE A hydraulic transmission for a clothes washer including a variable flow fluid pump with separate controls for the pump for each cycle of operation including a fluid pressure responsive piston to vary the spring load opposing movement of an element by said controls to vary the flow of the pump whereby the proper spring load is provided for each cycle.

A primary object of the invention is to provide a hydraulic pump control for a hydrostatic transmission in which means are provided to afford control of the transmission in a manner that there is an instant reaction to changes in pressure and thus overloading of the prime mover is prevented.

A further object of the invention is to provide a pump control in accordance with the preceding object in which stop means are provided to assure a predetermined minimum fluid flow from the vane pump when the prime mover is rotating at rated r.p.m. According to the pres ent invention the minimum fluid flow is sufiicient to actuate the controls so that the revolutions per minute selected and the operations per minute selected for the agitate cycle is signaled to the pump.

A further object of the invention is to provide a pump control system for a hydrostatic transmission in which means are provided for determining the revolutions per minute of the spin basket or the operations per minute of the agitator in response to the position of a pivotally eccentric ring which determines the volumetric displacement of the pump.

A further object of the invention is to provide spring means which cooperates with a manual setting to determine the position of the eccentric ring and in which means are provided responsive to pump output pressure for varying the spring loading as a function of the output pressure.

Another object of the invention is to provide a control system in accordance with the preceding objects in which pressure compensation means are provided to destroke the pump to a lower fluid flow during the washing of a heavier than normal load so that overloading of the prime mover is precluded.

Another object of the invention is to provide a transmission control in which overloading of the prime mover is precluded and in which the rate of spin is manually adjustable below a predetermined value so that water is pumped out of the tub before high speed spin is achieved and thus spilling of water from the tub is precluded.

The invention consists of the novel construction, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects and such other objects as will appear from the following description of the preferred embodiment of the invention illustrated with reference to the accompanying drawings 3,415,058 Patented Dec. 10, 1968 "ice FIGURE 2 is a view similar to FIGURE 1 but showing the speed control means in the position it assumes during the agitate operation.

The improved pump control herein disclosed is of a similar structure to that disclosed in copending application Ser. No. 538,436 filed Dec. 13, 1965, of common assignee and constitutes an improvement thereover.

Referring to the drawings and more particularly to FIGURE 1, the hydrostatic transmission of the present invention is indicated generally by reference numeral 10 and includes a vane type pump .12.

In FIGURE 1 the spin condition is illustrated in which conduit 16 is in the inlet and conduit 18 is the outlet conduit for the pump. The outlet conduit 18 in the condition of the system illustrated in FIGURE 1, supplies fluid under pressure to a spin fluid motor 20. As will be described more fully hereafter, when the transmission is in the agitate cycle as shown in FIGURE 2 conduit 16 is the outlet conduit supplying fluid under pressure to an agitator fluid motor 22 and conduit 18 is the inlet conduit. A check valve 13 connected to the sump is provided in conduit 18 and communicates fluid to conduit 18 when it is serving as the inlet conduit. A check valve 14 is provided in conduit 16 which communicates fluid to conduit .16 when conduit 16 is serving as the inlet conduit. A drain conduit 15 is provided for pump 12 which communicates any pump leakage back to the sump.

FIGURE 1 illustrates the condition of the present system during the spin cycle. In this condition, rotor 24 of the vane pump 12 is rotated in a counterclockwise direction by a reversible electric motor (not shown). The rotor 24 has a plurality of circumferentially spaced radial slots 26 in each of which is positioned a radially outwardly biased vane 28. The vanes 28 are urged into abutment with the inner periphery of a cam ring 30 which is pivotally mounted on a pin 32. The pump 12 further includes a pair of arcuate ports 34 and 36 which, as will be hereinafter apparent, serve as inlet or outlet ports depending upon the direction of rotation of the rotor 24. In the condition illustrated in FIGURE 1, the port 34 serves as an inlet port while the port 36 serves as an outlet port. In this condition, fluid flow to the agitator motor 22 is precluded by a check valve 38 having a single ball 40. The displacement of the pump 12, and consequently the speed of rotation of the fluid motor 20 depends upon the position of the ring 30. In FIGURE 1, the ring 30 is illustrated as being in the maximum displacement position. This position is effected by an actuator assembly 42, which bears against the left side of ring 30 as influenced by a pressure-compensated spring assembly 44 which bears against the right side of the ring 30.

The actuator assembly 42 includes a piston 46 slidably received in a bore 48 and a plunger 50 slidably received in the bore 48 and relatively movable axially with respect to the piston 46. The piston 46 has at the right end thereof a flange 52 received within a bore 54 of the plunger 50. Movement of the piston 46 to the left is limited by a screw 60. The position of plunger 50 with respect to the piston 46 is limited by a snap ring 56. Fluid under pressure is admitted to the bore 48 through a conduit 49 and acts against the right end of piston 46 to move the piston 46 to the left to a position determined by a screw 60 which is threadedly received in a housing 62 and may be rotated by a lever 64 which, in turn, may be actuated from the washer control panel by means of a bowden wire or the like. Fluid flowing past the piston 46 is drained to sump by means of a return 51. As the fluid under pressure flows into the bore 48 it passes around the flange 52 and pressurizes the left end of plunger 50 thus moving the plunger 50 until the snap ring 56 stops on flange 52, plunger 50 then serves as a stop for the left side of the cam ring 30. This establishes the maximum displacement stop position for the cam ring 30 which is biased into that position by means of the spring assembly 44.

The spring assembly 44 includes a housing 66 having a bore 68 in which is slidably disposed a piston 70. The bore 68 is in communication with ab ore 72, of less diameter which defines a shoulder 74. At the left side of the piston 70 is a hollow boss 76 against which abuts an outer spring 78 and an inner spring 80. The springs 78 and 80 cooperate to urge the cam ring 30 to the left. The shoulder 74 forms a stop for the piston 70 and thus the extent of compression of the springs 78 and 80 is limited.

According to an important feature of the present invention the loading of the springs 78 and 80 may be adjusted so as to be infinitely variable within limits depending upon the output pressure of the pump 12. This is accomplished by a fluid conduit 82 which aflords communication between the valve 38 and the right side of the piston 70 for movement of the piston 70 to the left to compress the springs 78 and 80, as will be more full described in the condition illustrated in FIGURE 2. Movement of the piston 70 to the right is adjustably limited by a screw 84 threadedly received in a fixed element 86. Pressure relief in the spin circuit is afforded by a relief valve 88.

Braking of the clothes basket is afforded by a brake valve 92 which is equivalent to that described in the above-mentioned copending application. When the brake valve 92 is actuated, fluid is returned to sump by means of conduit 94 and leakage by conduit 96.

In the spin cycle as illustrated in FIGURE 1 the lever 64 is adjusted for high speed operation, the output fluid pressure through conduit 82 will position the piston 70 and provide a spring loading of the assembly 44 as required correctly to move and hold the cam ring 30 against plunger 50. If the manual lever 64 is moved for low speed operation the piston 46 will be moved to the right slightly forcing the cam ring 30 to assume a decreased displacement position for the pump. Pressure compensation will not take place during the spin cycle because the piston 46 and plunger 50 have the same area. For spin operation the relief valve 88 limits maximum pressure and thus protects the electric motor (not shown).

In FIGURE 2 is illustrated the system of the present invention in condition for operation of the agitator motor 22. In this condition, port 36 serves as an inlet port while port 34 serves as an outlet port. The ball 40 of valve 38 is positioned to block conduit 18 while conduit 16 is pressurized for rotation of the motor 22. In this condition, the rotor 24 rotates in a clockwise direction, as indicated by the arrow, actuator 98 and piston 70 will be positioned in dependence upon the speed called for by manual adjustment of the pump displacement, and the wash load fluid under pressure spreads piston 100 and plunger 106 to act on the left side of and thus limit travel of ring 30. Ring 30 is pushed to the left against stop formed by the plunger 106, piston 100, and the screw adjustment 108.

In FIGURE 2 high speed operation has been selected by the operator and the springs 78 and 80 are shown with additional load to provide pressure compensation at an increased value. An actuator assembly 98 is provided and includes a piston 100 having an end flange 102 received within a bore 104 of a plunger 106. A screw 108 provides an adjustable left limit stop for the piston 100 and may be rotated by means of a lever 110. The actuator assembly 98 is energized by fluid that flows into bore 112 through conduit 114 from conduit 16. Fluid flowing past the piston 100 is drained to sump by means of a return 113. As in the case of actuator assembly 42, the plunger 106 moves into abutment with the left edge of the cam ring 30 as the springs 78 and 80, with additional bias, bear against the right edge of the cam ring 30.

The bore 112 is stepped so that the right end is of greater diameter than the left end and the cro i n l areas forcing the plunger 106 to the right exceed the cross sectional area of the right side of the piston 100. The net effect is that the plunger 106 will move to the right pulling piston as the pressure increases beyond a certain value to act as a pressure compensation since it is a force tending to move cam ring 30 toward a zero displacement position.

The actuator assemblies 42 and 98 of the present invention are advantageously arranged to provide one range of pressures for the spin cycle and a different range of pressures for the agitate cycle. Since greater pressures are necessary for agitation, the system is designed to provide this increased pressure while maintaining the pump at the optimum displacement condition for both the spin and agitate cycles.

The control system of the present invention exhibits important advantages over control systems of this general type heretofore known. For instance, the present system is carefully balanced to react to minute changes in pressure and thus overloading of the driving motor is prevented. The screw 84 provides a minimum stop to afford minimum fluid flow and pressure suflicient to actuate the fluid circuits in response to preset limits imposed by the actuator assemblies 42 or 98. The spring assembly 44 reacts in dependence upon manual speed setting and affords a light spring force with low fluid pres sure and a high spring force with high fluid pressure. By this arrangement the flow is reduced automatically during agitation as the pump builds up excessive pressure, such as during the washing of a heavy overload of clothes, the cam ring 30 moving to a position of decreased displacement by movement of the plunger 106 to the right.

Various of the features of the invention have been particularly shown and described; however, it should be obvious to one skilled in the art that various modifications may be made therein without departing from the scope of the invention.

We claim:

1. A hydraulic transmission including a vane pump having a movable element adapted to vary the displacement thereof when moved, a pair of fluid motors driven by said pump, reversible means for driving said pump in one direction or the other to supply fluid under pressure to one fluid motor or the other, means for controlling the output of said pump to prevent overloading of said driving means, said last-named means including means for manually selectively supplying fluid under pressure to either of said fluid motors over a predetermined range of pressures, said control means further including means for varying the displacement of said pump over a differing range of pressure when said pump is supplying fluid to the other of said fluid motors.

2. A transmission in accordance with claim 1 wherein said control means includes means, including spring means for adjusting the position of said movable element and wherein means are provided for varying the loading of said spring means in response to the fluid pressure at the output side of said pump.

3. A transmission in accordance with claim 2 wherein said control means includes a slidable piston and wherein means are provided to afford fluid communication between the pump outlet and one side of said piston for compressing said spring in proportion to the level of fluid pressure at the pump outlet.

4. A transmission in accordance with claim 3 wherein said control means is operative to afford relief when the fluid pressure exceeds a predetermined value despite the positioning of said manually selective means.

5. In a hydraulic transmission, a variable volume fluid pump having a movable element adapted to vary the dis placement of said pump when moved, a pair of fluid motors adapted to be operated at dilferent speeds, means for driving said pump in either direction of rotation for selectively actuating either of said fluid motors, control means for selectively supplying fluid under pressure at a relatively high pressure to one of said motors or fluid at relatively low pressure to the other of said motors, said control means being manually adjustable within preselected limits and having means for relieving excessive fluid pressure despite the manual setting.

6. A transmission in accordance with claim 5 wherein said control means includes spring means whose loading may be varied to vary the range of output pressure.

7. A transmission in accordance with claim 6 wherein means are provided for limiting the minimum fluid output of the pump.

8. A transmission in accordance with claim 7 wherein spring means are provided to assist in positioning said movable element and wherein stop means are provided to limit the minimum effective position of said spring means.

9. A transmission in accordance with claim 8 wherein said movable element is moved to one position for low speed operation of one of said fluid motors and to an other position for high speed operation of the other of said fluid motors and wherein means are provided for relieving pump output pressure when it reaches a predetermined value.

10. A transmission in accordance with claim 9 wherein a pair of fluid actuators are provided to move said movable element into one or the other displacement conditions in opposition to the spring pressure in that particular condition, in which one or the other actuator becomes operative in response to movement of said manual means and continues to control displacement of the pump even if the manual means setting is charged.

No references cited.

EDGAR W. GEOGHEGAN, Primary Examiner.

U.S. C1. X.R. 

